+ int ret;
+
+# if PTHREAD_SIGMASK_INEFFECTIVE
+ sigset_t omask, omask_copy;
+ sigset_t *old_mask_ptr = &omask;
+ sigemptyset (&omask);
+ /* Add a signal unlikely to be blocked, so that OMASK_COPY
+ is unlikely to match the actual mask. */
+ sigaddset (&omask, SIGILL);
+ memcpy (&omask_copy, &omask, sizeof omask);
+# else
+ sigset_t *old_mask_ptr = old_mask;
+# endif
+
+ ret = pthread_sigmask (how, new_mask, old_mask_ptr);
+